Alone in space? Study investigates the effects of isolation
July 3, 2025 | SOLIS8 – eight-day ESA isolation study at :envihab
Alone in space? Study investigates the effects of isolation
Privacy only found in the sleeping pod
As part of ESA's SOLIS8 isolation study, three men and three women simulated a space mission for eight days. Participants had their own sleeping cabins within the module – the only areas besides the toilets that were not monitored by cameras. The study, conducted at DLR's :envihab facility, is preparation for a 100-day isolation study in 2026.
A task during the study – docking with a virtual spacecraft
Participants followed a fixed schedule with different tasks. Among other activities, they had to dock a virtual space capsule with a spacecraft. The experiment simulates six degrees of freedom – like in microgravity. As part of ESA's SOLIS8 isolation study, three men and three women simulated a space mission for eight days. The study, conducted at DLR's :envihab facility, is preparation for a 100-day isolation study in 2026.
The door stayed closed – no outside contact with the outside world
The M5 module, where ESA's SOLIS8 study took place and SOLIS100 will be conducted, was specially developed for long-term studies on humans in an artificially controlled, isolated and confined environment. The module can accommodate up to six people. As part of the SOLIS8 isolation study, three men and three women simulated a space mission for eight days. The study, conducted at DLR's :envihab facility, is preparation for a 100-day isolation study in 2026.
Six volunteers – three men and three women – have spent eight days simulating a space mission: in confined conditions, with minimal contact with the outside world and following a strict schedule.
Findings on the psychological and physical effects will inform a 100-day isolation study planned for 2026, which will also be conducted by DLR at :envihab.
Participants must meet criteria similar to those required of astronauts.
Focus: Space, exploration, space medicine
What effects do long-duration missions have on astronauts? How do they cope with confined spaces, isolation or the feeling of being completely cut off from Earth? These and many other questions will be addressed next year in the SOLIS100 study, which will be conducted by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). The study, led by the European Space Agency (ESA), will run for 100 days. The preparatory SOLIS8 isolation study has now concluded, laying the groundwork for the longer investigation.
Three men and three women spent eight days in a sealed-off area at :envihab (its name coming from the words 'environment' and 'habitat') – part of the DLR Institute of Aerospace Medicine in Cologne. :envihab features a special module for long-term studies in a controlled and isolated environment. As with a space station, everything needed for living and scientific experiments is available within this compact space. DLR will also conduct the ESA SOLIS100 study in the same module. Through this pilot study, researchers have tested the equipment, procedures and protocols for the main investigation.
Naps forbidden, daily exercise mandatory
The six participants largely went without daylight and contact with the outside world for the entire eight days. They prepared meals from pre-packaged and stored food, slept in individual capsules and followed a strict schedule for all activities. Specific time slots were allocated for sleep, meals and leisure activities. For instance, naps during waking hours were prohibited, except during the day-and-a-half of 'free time'. Rules governing personal belongings mirrored those of the International Space Station ISS: items must not exceed 1.5 kilograms and had to fit into a box measuring 12.7 by 20.32 by 5.08 centimetres (five by eight by two inches). Additional restrictions included: only two five-minute showers per week, limited clothing and laundry, and rationed food. As with astronauts, daily physical training formed part of the programme to counteract adverse effects on muscles, bones and the cardiovascular system.
The DLR project team monitored the participants around the clock to ensure their safety – but also to observe crew behaviour and collect data. To minimise outside contact, blood samples were taken through a device in the door: participants extended their arms without making eye contact. Instructions and routines were communicated through short audio briefings. Unlike during a real space mission, however, emergency medical and psychological support was available at all times.
Why conduct isolation studies at all?
Human space exploration is set to extend far beyond the Space Station in the future. There are plans for missions to the Moon and Mars, and for establishing a lunar base. "These missions will bring new psychological and physical challenges," says Jens Jordan, Director of the DLR Institute of Aerospace Medicine. "Travel times will be longer and crews will require greater autonomy in isolated and confined environments. High-quality studies are essential to understand and overcome these challenges."
Isolation studies have long served as analogues for space missions, investigating how conditions affect crew health, behaviour and performance. "However, current data is limited," adds Sarah Piechowski-Worms, scientific lead of the SOLIS8 study. "Further research under controlled conditions is therefore necessary to better understand the psychological and physiological effects. This research will help predict risks, improve crew selection and training, and develop strategies to maintain performance and health during long-duration missions." The findings from SOLIS8 will be evaluated in the coming weeks.
"ESA's isolation studies address urgent questions for future space missions and offer European research teams the opportunity to pursue their own research questions," says Ann-Kathrin Vlacil, team leader for ESA's science programme for human spaceflight. "These studies help to better understand the psychological and physiological effects of long-duration missions. They also contribute to improving the selection and training of future astronauts."
Complex selection process
The DLR study team selected the SOLIS8 participants through a multi-stage process, which will be expanded for SOLIS100. Due to the longer isolation period, additional requirements will apply. The SOLIS100 study will last approximately four months, with 100 days in isolation. Before selecting the SOLIS100 crew and backup crew, questionnaires and personal interviews will be followed by medical examinations and psychological screening, conducted both individually and in groups. The selection process will begin shortly.
Applicants must meet numerous criteria that also apply to astronauts. Among other requirements, they must be between 30 and 55 years old and in good health, have a body mass index (BMI) between 18.5 and 30, and be able to speak and understand English to at least B2 level. They should also hold a university degree. More criteria and details on the process will be available on the website dlr-probandensuche.de (in German) once applications open.
The :envihab aerospace medicine research facility in Cologne
What would happen to the human body during a flight to Mars? How do patients' bodies react when confined to bed for extended periods? How does lighting affect our mood? Are there measures to counteract resulting adverse effects? Answers to these questions are also important here on Earth, for example to better understand the effects of ageing, prolonged bed rest, immobilisation and isolation.
The DLR Institute of Aerospace Medicine is a world-leading research institute in this field. At its unique :envihab medical research facility, the institute carries out pioneering research into preserving human health and performance. Within the 3500 square-metre facility, the effects of extreme environmental conditions on humans – and possible countermeasures – are investigated.
The M5 module – where the SOLIS8 study took place and SOLIS100 will be conducted – was specially developed for long-term studies on humans in a controlled, isolated and confined environment. The module can accommodate up to six crew members to simulate a space mission. It features monitoring technology, separate rooms for storage, food preparation, medical treatment, confidential communication and sanitary facilities. The main area comprises private crew quarters and communal areas. The :envihab facility thus offers a platform for exploring novel research questions and conducting complex studies under realistic conditions with a high degree of precision – ideal for current research as well as future innovations in space medicine.
The SOLIS8 study was the first to use fitness watches for health monitoring. For this, the DLR Institute of Aerospace Medicine collaborated with the companies adesso and Samsung Germany. Health data was recorded locally and was encrypted and processed without cloud access to ensure data privacy as well as enabling continuous, comprehensive monitoring of participants' vital signs in isolated environments.
